Antiviral activity of the pregnancy recognition hormone ovine trophoblast protein-1

Ovine trophoblast protein-1 (oTP-1) is an antiluteolytic protein which plays an important role in maternal recognition of pregnancy. It exhibits a 45-70% amino acid sequence homology with alpha interferons (IFN-alpha s) from various species. We show here that purified oTP-1 has high specific antiviral activity (2-3 X 10(8) units/mg protein) and is thus as potent as any known IFN. oTP-1 is antigenically distinct but does show antigenic relation to both ovine and bovine IFN-alpha s. The antiviral activity of oTP-1 could be demonstrated in Day 12 - Day 16 conceptus culture medium and in allantoic fluid from Day 60 of pregnancy. Our functional and antigenic characterization suggests that oTP-1 is a type of IFN-alpha which performs classic roles associated with IFN-alpha, as well as being the primary conceptus secretory product responsible for maternal recognition of pregnancy.